By 2050, the world’s population is projected to increase from 6.7 billion to 9.2 billion, according to a just-released United Nations (UN) assessment. Declining fertility rates and increased longevity will lead to an aging population, the UN predicts in World Population Prospects: The 2006 Revision, which offers high, medium, and low projections of population change in each country. The projections are made with the assumption that fertility will continue to decline in the developing world and that efforts to both treat AIDS patients and prevent the spread of human immunodeficiency virus (HIV) will expand.

The projected 2.5 billion increase by mid-century is the equivalent of the entire world population of 1950, and developing countries will bear nearly all the net growth, according to the UN. The total population in these countries is projected to rise from 5.4 billion in 2007 to 7.9 billion in 2050. The industrialized world is expected to maintain its existing population of 1.2 billion through 2050—even with anticipated net immigration of 2.3 million people annually—and to nearly double its population aged 60 and over.

In these projections, fertility in less-developed countries is assumed to decline from 2.8 children per woman in 2005­–2010 to 2.1 children per woman in 2045–2050—roughly the number that would eventually stabilize a population with no net migration. The UN demographers assume as well that in the 50 least-developed countries fertility drops even more dramatically, from 4.6 children per woman to 2.5. If fertility rates of 2000–2005 were to remain the same, the population of the world’s less-developed regions would increase to 10.6 billion instead of 7.9 billion. Without continued reductions in fertility, the world population could increase by twice as many people as were alive in 1950.

The UN projections also assume there will be a major increase in the proportion of AIDS patients who receive antiretroviral therapy, as well as growing success in slowing the spread of HIV. It is assumed that, by 2015, 31 of the most AIDS-affected countries will manage to provide antiretroviral treatment to at least 70 percent of those infected with HIV in each country. In countries less affected by the HIV/AIDS pandemic, treatment levels are expected to reach only 40 to 50 percent of those infected by 2015. Demographers also assume that patients receiving treatment will survive 17.5 years instead of the 10 years expected for untreated patients, a measure of the effectiveness of antiretroviral therapy in prolonging life.

“The big news of this report is that the international commitment to treat people with HIV/AIDS in developing countries has been successful enough that demographers have revised upward their estimates of average life expectancy in places like sub-Saharan Africa,” says population expert and Worldwatch Institute vice president Robert Engelman. “But governments will have to invest significantly in family planning programs for even the medium projection to be realized.”

Alana Herro writes for Eye on Earth (e²), a service of World Watch Magazine in partnership with the blue moon fund. e² provides a unique perspective on current events, newly released studies, and important global trends.

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